You can "lose" your claim if the person who claimed it dies. Not sure if it still keeps the claim should others in your party still have sufficient hate, but in 21 Diadems I have yet to see a single red claim not drop a chest unless we legitimately lost the claim to the mob. Also, tracks != claims, not sure if perhaps those two who were stating as such were aware of that. You don't get instant claim of a mob you spawn via tracks (although I do feel you should).